Transport systems are used to transport articles accommodating semiconductor wafers or reticles, for example, in a semiconductor device manufacturing factory or the like (see International Publication No. 2013/150859, for example). That transport system includes an overhead transport vehicle that transports articles and a stacker crane that delivers and receives the articles to and from a storage rack. The overhead transport vehicle transports an article to a load port of a processing tool such as a semiconductor manufacturing apparatus, for example. The storage rack is arranged in the vicinity of the processing tool such as a semiconductor manufacturing apparatus and, when an article is already present on the load port, the overhead transport vehicle transports the article to the uppermost shelf of the storage rack, for example. The stacker crane places the article that has been transported onto the uppermost shelf of the storage rack onto another shelf, or transfers articles between the storage rack and the load port, for example.
When the length of time required to deliver and receive an article to and from the load port is long with the transport system as mentioned above, the operation rate of the processing tool is reduced. For example, if the load port is filled with articles waiting to be transported out, the processing tool cannot have a new article transported into the load port, causing the operation rate to decrease. Also, when there is no article on the load port at the time of shifting to the next processing, the processing tool waits until an article has been transported onto the load port, causing the operation rate to decrease.
In view of the above circumstances, it could be helpful to provide a transport system capable of quickly delivering and receiving articles to and from a processing tool.